An Approach to Simulating Sediment Management in the Mekong River Basin

The Mekong/Lancang River Basin in Southeast Asia is undergoing a period of rapid hydropower development. Newly constructed dams will trap ecologically valuable sediments, which transport nutrients and maintain the river’s morphology. Sediments trapped behind hydropower dams could significantly impact the basin’s exceptional biodiversity and food production that support many of those living in the basin. This paper introduces an approach for estimating the potential impact of reservoirs on the basin’s sediment regime, as well as the potential for various forms of reservoir sediment management to improve sediment passage through and around dams. Our sediment simulation model, SedSim, predicts in relative terms the spatial and temporal accumulation and depletion of sediment in river reaches and in reservoirs under different reservoir siting, design and operating policies. The model identifies the relative tradeoffs between hydropower production, and flow and sediment regime alteration, associated with reservoir sediment management techniques, including flushing, sluicing, bypassing, density current venting and dredging. While developed for and applied in the Mekong River basin, this approach may be of interest to those facing similar sediment management challenges in other data-scarce regions.